axial projection

(redirected from base projection)

ax·i·al pro·jec·tion

radiographic projection devised to obtain direct visualization of the base of the skull.

axial projection

; axial view radiographic projection to visualize sesamoid bones within the tendon of extensor hallucis brevis at the plantar aspect of the first metatarsophalangeal joint, with the foot placed in a position simulating toe off (see Table 1)
Table 1: Common radiographic projections of the foot and ankle
ProjectionVisualization
Foot projections
Dorsiplantar (DP) projection or anteroposterior (AP) viewWeight-bearing with the beam directed at 15° to the frontal plane, to eliminate distortion due to the angulation of the metatarsals and centred on the metatarsal shafts
It is used to visualize the phalanges, metatarsophalangeal joints, the metatarsals and the midfoot
Lateromedial oblique projectionWeight-bearing with the beam angled at 45° to the lateral side of the sagittal plane and centred on the forefoot; or non-weight-bearing, with the beam vertical and foot everted so that the plantar surface is at 45° to the ground surface
It is used to visualize the phalanges, metatarsals, metatarsocuneiform joints and sesamoids, but tends to give an elongated image of bony architecture
Mediolateral oblique projectionWeight-bearing with the beam angled between 25 and 45° to the medial side of the sagittal plane and centred on the forefoot
It is used to visualize the first ray and associated structures, but tends to give an elongated image of bony architecture
Lateral projectionWeight-bearing or non-weight-bearing, with the beam angled at 90° to the lateral aspect of the foot and centred on the mid- or hindfoot
It is used to visualize the profile of the whole foot, but obscures the midtarsal joint, due to superimposition of local structures
Digital projectionThe lateromedial oblique projection is useful to visualize subungual exostoses, especially when the hallux (or affected toe) is raised up on a pad
Sesamoid projection or skyline projectionWeight-bearing, with the metatarsophalangeal joints dorsiflexed to 45° and the beam angled to be parallel to the ground surface on the sagittal plane, and centred on the plantar aspect of the forefoot
It is used to visualize the relationship of the sesamoids with the head of the first metatarsal
Tarsal and ankle projections
Anteroposterior viewWeight-bearing with the beam angled at 90° to the frontal plane and the beam centred on the ankle joint
Used to visualize the ankle mortise and the trochlear surface of the talus
Axial calcaneal projectionWeight-bearing with the beam angled at 45° to the posterior aspect of the sagittal plane with the beam centred on the hindfoot
It is used to visualize calcaneal trauma
Harris-Beath projectionSimilar to the axial calcaneal projection, but the patient is positioned as if making a ski-jump, that is, weight-bearing with the foot dorsiflexed at the ankle and the beam angled at 45° to the posterior aspect of the sagittal plane with the beam centred on the ankle
It is used to visualize the subtalar joint where talar fusions are suspected
References in periodicals archive ?
According to an IMF base projection, Saudi, which is the largest Arab economy, is anticipated to face a budget deficit of 0.
With the base projection complete, the next step in projecting the long-term prison population was to estimate the effects that new policies and programs might have.
Failure to base projection on and/or anchor projection by cold hard facts
Line 2 shows the effect on the Base projection from changing the assumption about the differential in the effective rate of return on direct investment, reducing the Base case spread of 4.
s] is the moving average coefficient matrix associated with the structural shocks in the [epsilon] vector, the second term on the right-hand side is the dynamic forecast or base projection, and the first term on the right-hand side is the j-period-ahead forecast error.
Historical decompositions assign credit to the shocks to the variables in the system for the difference between what can be labeled the base projection for a series and the actual series.
Conversely, spending as a share of nominal GNP shows the opposite relationship: high-trend government spending accounts for a smaller proportion of GNP and low-growth government spending a higher proportion of GNP than in the base projection.
t +j] given information available at time t, the so-called base projections of the elements of the vector Y,(8) and where the first term on the right hand side shows the difference between the actual series and this base projection due to innovations in the variables subsequent to period t.
As noted by Burbidge and Harrison |1985~, the historical decomposition assigns credit for the difference between what can be called the base projection for a series and the actual series to the shocks to the system's variables.
Thus, the exogenous value was increased by 10 percent in each year of the period, a model solution was generated, and the results were compared with the results of the base projection.
Along each base scenario, the projection stops at each recalculation point to perform a set of nested calculations to assess a value before continuing on with the base projection.
Further, inclusion of the variance of income as the measure of income uncertainty reduces the root-mean-square error of the base projection by an average of 33 percent.